1. Field of the Invention
The present invention relates to a lead frame with a heat spreader, and a semiconductor package using the same.
2. Background of the Related Art
In general, a semiconductor packaging process is conducted in the manner described below using a lead frame. First, after fabrication of integrated circuits on a wafer, the wafer is separated into individual chips. Next, chip bonding is performed. As shown in FIG. 1A, during the chip bonding process each of the separated chips is attached to a die pad 14 of a lead frame with an epoxy 8. Wire bonding is then performed, during which, bonding pads 5 on the chip 4 and inner leads 2 of the lead frame are electrically connected with a conductive connecting member 6, which is typically gold wire. Then, a molding process is conducted, and the chip, the connecting members 6, the die pad 14 and the inner leads 2 are encapsulated for protection with an epoxy molding compound 10. Then, after the molding, tie bars and dam bars of the lead frame may be trimmed or cut off and the outer leads may be bent into a required form. The result is a semiconductor package as shown in FIG. 1A. The die pad 14 on the center of the lead frame, which is attached to a semiconductor chip, may also be called a paddle.
FIG. 1B illustrates a semiconductor package with a heat spreader. The heat spreader 3 is attached under the inner leads 2 with an insulative adhesive 7. A semiconductor chip 4 is attached to the heat spreader 3 with an epoxy 8. Conductive connecting members 6 of wire are used to electrically connect bonding pads 5 on the chip 4 to the inner leads 2. A molding compound 10 encapsulates the chip 4, the connecting members 6, the heat spreader 3 and the inner leads 2.
In the semiconductor package shown in FIG. 1B, the heat spreader 3 takes the role of the die pad of a lead frame as shown in FIG. 1B. However, in the semiconductor package as shown in FIG. 1B, the heat spreader 3 extends underneath the inner leads 2. A maximum size of a chip mountable on the heat spreader 3 is limited to the distance between the inner leads 2, as shown in FIG. 2.
When the chip size exceeds the maximum dimension shown in dotted lines in FIG. 2, a new lead frame with a larger heat spreader must be developed. Because the development of a new lead frame takes a long time (more than 5 months), and application of the new lead frame to a production line is impossible during the time of development, a deadlock in the production is caused. Also, frequent re-arrangement of a production line to accommodate different size lead frames increases costs and reduces productivity.